Recently, as the redevelopment of urban areas and the large-scale reconstruction of dilapidated apartments are actively conducted, a large amount of construction waste is generated every year, and it is expected that the generation of such construction waste will further increase in the future.
However, such construction waste is mostly buried in the ground without being treated or is thrown away, which causes severe soil contamination. For this reason, various attempts to recycle the construction waste are currently being made, but the proportion of construction waste being recycled is very insignificant, so that only a small amount of the construction waste is recycled as material or filler for forming roadbeds in road construction.
In one example of the prior methods for separating the construction waste into components, recyclable aggregate is ultimately recovered through the following various processes.
Collected construction waste is first crushed through a jaw crusher, and impurities, such as steel reinforcing members, contained in the crushed construction waste, are removed by magnetic separation.
Also, impurities, such as vinyl, paper, styrene foam and wood debris, are removed through air separation, and the remaining material is subjected to second and third crushing steps using a cone crusher, a roll crusher and/or an impact crusher.
The crushed material is then separated into components according to particle size. Finally, the remaining material is subjected to a separation process using an aerated water tank, in which still more impurities, which float on water are removed so as to recover recyclable aggregate.
However, even when the separation process using the aerated water tank is carried out, it is impossible to remove wood debris, red bricks, tiles, asphalt concrete, cement paste, etc, by specific gravity separation using water, because they have a specific gravity higher than 1 (the specific gravity of water).
As a result, the recovered recyclable aggregate contains significantly large amounts of impurities, such as cement paste, asphalt concrete, red bricks, tiles and cement paste, which cause an increase in water absorption and a reduction in specific gravity, resulting in reduced strength. The recovered recyclable aggregate is regarded as low-grade aggregate, so its use is limited to material for road base layers, etc.
Accordingly, there is an urgent need for the development of a separation method capable of recovering only good-quality recyclable aggregate by accurately separating recyclable aggregate from the asphalt concrete, red bricks, tiles and cement paste contained in construction waste.